1. Field of the Invention
The present invention relates to a method of making a narrow pole tip by ion beam deposition and, more particularly, to such a method wherein a forming layer provides a side wall where pole tip material is ion beam deposited.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The suspension arm urges the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic field signals from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
A write head typically employs ferromagnetic first and second pole pieces which are capable of carrying flux signals for the purpose of writing the magnetic impressions into the track. Each of the first and second pole pieces has a pole tip, a yoke and a back gap with the yoke being located between the pole tip and the back gap. The pole tips are located at the ABS and the back gaps are magnetically connected at a recessed location within the write head. At least one coil layer is embedded in an insulation stack between the yokes of the first and second pole pieces. A nonmagnetic write gap layer is located between the pole tips. Processing circuitry digitally energizes the write coil which induces flux signals into the first and second pole pieces. The flux signals bridge across the write gap layer at the ABS so as to write the aforementioned magnetic impressions or bits into the track of the rotating disk. The thinner the thickness of the write gap layer, the greater the number of bits the write head can write into the track.
A write head is typically rated by its real density which is a product of its linear bit density and its track width density. The linear bit density, which is dependent on the thickness of the write gap layer and the data rate of the write head, is the number of bits which can be written per linear inch along the track of the rotating magnetic disk and the track width density, which is dependent on the track width of the write head, is the number of tracks that can be written per inch along a radius of the rotating magnetic disk. The linear bit density is quantified as bits per inch (BPI) and the track width density is quantified as tracks per inch (TPI). The width of the last pole tip to pass along a track of a rotating magnetic disk determines the track width density. The more narrow the pole tip the higher the tracks per inch (TPI). Efforts over the years to increase the real density of write heads have resulted in computer storage capacities which have increased from kilobytes to megabytes to gigabytes.
The first and second pole pieces are typically fabricated by frame plating. Photoresist is employed to provide the frame and a seed layer is employed to provide a return path for the plating operation. A typical sequence for fabricating a pole piece is to sputter clean the wafer, sputter deposit a seed layer, such as nickel iron, on the wafer, spin a layer of photoresist on the wafer, light-image the photoresist layer through a mask to expose areas of the photoresist that are to be removed (assuming that the photoresist is a positive photoresist), develop the photoresist to remove the light-exposed areas to provide an opening in the photoresist and then plate the pole piece in the opening up to a desired height.
The last pole tip to pass the aforementioned track on the rotating disk is typically the second pole tip (P2T) which is magnetically connected to the second pole piece. A typical method of making the second pole tip is to frame plate the second pole piece and its second pole tip as one layer. Unfortunately, this has resulted in a second pole tip with irregularly shaped first and second side walls due to pole tip notching. Pole tip notching is caused by light reflected from a high profile of the insulation stack into the pole tip region. In order to overcome this problem the second pole tip has been fabricated by a frame plating process followed by fabricating the remainder of the second pole piece with a second frame plating process. Even in this method the smoothness of the first and second side walls of the second pole tip depends upon the thickness of the photoresist employed to provide the frame for plating. When the opening in the frame is narrow in order to construct a narrow pole tip the resist frame must be high in order to permit sufficient pole material to be deposited so as to provide sufficient ferromagnetic material to carry the flux that writes the magnetic bits into the rotating magnetic disk. When the photoresist frame is thick the light exposure step loses a considerable amount of resolution before the light reaches the bottom of the photoresist layer. Accordingly, the width of the second pole tip is limited by this process. When the last pole tip to pass the rotating magnetic disk is the pole tip (P1T) of the first pole piece, the first pole piece and the first pole tip are also made with a single frame plating process. The problem with obtaining a narrow first pole tip is the same as that addressed hereinabove in obtaining a narrow second pole tip with a single frame plating process.